1. Field of the Invention
This invention relates to roofing systems, in particular insulated roofing systems.
2. Description of the Prior Art
Various roofing systems are known both for flat and sloped roofs to insulate and waterproof the roof. On flat roofs the most common roofing system for waterproofing is a built up laminar structure comprising a plurality of felt layers with each layer or series of layers over-laid with a hot bituminous (tar) composition to bind the felt to the roof. A layer of gravel tops off the structure. However elevated roof temperatures will cause cracking, vapor blisters, splitting or ridging. In addition the gravel has a tendency to sink into tie bituminous material during hot summer months. All of these factors result in standing water eventually seeping though the tar and gravel coating requiring a new roof to be installed. In recent years, as the advantages of applying insulation on the exterior as opposed to the interior of the roof deck have become known, the built up roof structure has been applied over insulation materials, typically sheets of insulation material. This created new problems as the insulating materials had poor mechanical properties had seams where water could seep through, needed to be fastened to the roof deck, are subject to degradation by UV radiation and absorbed moisture. In addition the built up roof systems are very labour intensive making them less economical. Numerous attempts have been made unsuccessfully to solve one or more of these problems. For example see U.S. Pat. No. 4,016,323; 4,021,981; 4,087,296; 4,212,913; 4,374,687: 4,668,315 and 4,837,095.
A common insulted roofing system in use today is that shown in U.S. Pat. No. 5,251,416. This system utilizes a series of foam insulation board panels with a thin rubber membrane bonded to the top surface of each board to render the insulation waterproof. The panels are mechanically fastened to the roof substrate. Rubber strips are applied with adhesive to overlap Joints between panels and the fasteners adjacent the joints. This system has a number of drawbacks. First if the rubber membrane is pierced the insulation board soaks up water and eventually the roof will leak. Secondly the joints between panels break down as the urethane foam commonly used absorbs moisture. Life expectancy of the roof is 4 to 5 years. The roof is entirely dependent on the thin membrane, which is approximately 10% of cost of roof to provide waterproofing.
For roofs with positive drainage, a sprayed on insulation foam has been utilized. A waterproof coating is then sprayed on top of the foam. This eliminates the problems experienced with mechanical fastening of panels however the system has not proven practical with relatively flat roofs. Any standing water will break down the coating and ultimately the foam. In addition the sprayed insulation foam cannot be applied over a conventional built up tar and gravel roof so the tar and gravel substrate needs to be removed before applying the new roof. This eliminates any cost savings over the use of mechanically fastened panels. In addition while the sprayed in place foam insulation is 90% closed cell (as opposed to open cell foam panels) and therefore provides some waterproofing, standing water and UV radiation will break it down. In addition the sprayed in place foam and coating systems do not stand up in cold climates. Installing sprayed in place urethane roofing foam over steel roofing with positive drainage has worked well. However sprayed in place urethane foam applied over flat roofs to manufacturers specifications after two or three years starts developing cracks due to cold climate and effects of standing water. While numerous coatings have been proposed none has provided an efficient and reliable waterproof and U.V. protection for the foam. Foamed in place urethane roofing due to the unavailability of an effective coating has not be approved or specified by engineers.
It is an object of the invention to provide an energy efficient, economical and dependable insulated roofing system.
It is a further object of the invention to provide an insulated roofing system that can be installed over existing tar and gravel substrate without removing the existing roofing.
Thus in accordance with the present invention there is provided an insulated roofing system comprising a closed cell, foamed in place insulation applied over the roof deck or existing substrate. In the preferred embodiment the foamed in place insulation is selected from foamed synthetic resins made of polystyrene, polyethylene, acrylic resin, phenol resin, urea resin, epoxy resin, diallylphthalate resin, urethane resin and the like. The preferred foamed in place insulation is polyurethane foam. A rubber membrane is fully adhered over the insulation by an adhesive. The rubber membrane is selected from natural or synthetic rubbers such as styrene-butadiene rubber, acrylonitrile-butadiene rubber, chloroprene rubber, butadiene rubber, isoprene rubber, butyl rubber, ethylene-propylene rubber, ethylene-propylene diene mar (E.P.D.M.), polyisobutylene, styrene-butadiene-styrene block copolymer, styrene-isoprene-styrene block copolymer, chlorinated polyethylene, ethylene-vinyl acetate copolymer and the like either alone or in combination. The rubber membrane is preferably 45-60 mil thick E.P.D.M. The adhesive preferably consists of a slower curing adhesive that will permit the rubber membrane to be placed over the insulation and adjustments made to smooth it out before the adhesive cures. In the preferred embodiment a urethane foam adhesive with a cure time of about 20 minutes is sprayed over the foamed in place insulation.
In another embodiment the present invention comprises a method to apply an insulated roofing system comprising the following steps : (a) first clean the roof substrate (b) then foaming in place a closed cell roofing foam insulation (c) next applying a slow acting adhesive to the surface of the foamed in place insulation (d) then rolling a rubber membrane over the adhesive and (e) then smoothing out or adjusting the membrane to fully cover and be adhered to the foam insulation.
Further features of the invention will be described or will become apparent in the course of the following detailed description.